Two liquids at temperature 60° C and 20° C respectively have masses in the ratio 3:4 and the specific heats in the ratio 4:5, if they are mixed the resultant temperature is:

From Principle of method of mixtures,heat lost by hot liquid = heat gained by cold liquid.given masses in the ratio=3:4specific heats in the ratio=4:5let hot liquid mass =3m, specific heat =4cnow cold liquid mass=4m, specific heat =5cheat lost by hot liquid = m C∆T=3m(4c)(60-θ)heat gain by cold liquid =m C∆T=4m(5c)(θ-20)   heat lost by hot liquid =heat gain by cold liquid 3m(4c)(60-θ)=4m(5c)(θ-20) ⇒θ=350C